1. Field of the Invention
This invention relates to a rotary oil damper to be used in a push-open type member such as, for example, an ashtray in an automobile or an opening-shutting lid in a household electric appliance which is constantly urged in the opening direction for the purpose of braking the speed at which the push-open type member is opened.
2. Description of the Prior Art
This type of conventional oil damper is generally provided, as disclosed in Japanese Utility Model Public Disclosure No. 59-88548, with a housing incorporating therein a storing chamber open on one lateral side, a cap for shutting the opening in the storing chamber of the housing, a rotor disposed rotatably in the storing chamber of the housing, and a toothed wheel fixed to the leading end of a shaft of the rotor protruding outwardly through a cap hole. The storing chamber of the housing is filled with viscous oil such as silicone oil in conjunction with the rotor.
The application of this oil damper to the aforementioned push-open type ashtray in an automobile is accomplished by fixing the housing of the oil damper to either of the case of the ashtray and the frame retaining the ashtray case in an emerging-submerging manner, providing the remainder of the two components just mentioned with a rack, and allowing the toothed wheel on the damper side to be meshed with the rack as disclosed in Japanese Patent Public Disclosure No. 63-196258. As a result, the ashtray case tends to move in the opening direction by virtue of the resilient pressure and, in consequence of this motion of the ashtray case, the rotor rotates in spite of the viscous resistance of the oil inside the storing chamber of the housing. Thus, the opening speed of the ashtray case is braked and the ashtray case is enable to move slowly in the opening direction.
Indeed, the conventional oil damper is capable of braking the opening speed of the ashtray case and causing it to open slowly. Conversely, when the ashtray case is pushed into the frame, the braking force similarly derived from the viscous resistance of the oil is suffered to manifest its effect because of the construction of the oil damper. In this case, the viscous resistance of the oil entails the mischief that the ashtray case cannot be smoothly pushed into the frame.
An attempt to vary the torque of rotation of the rotor necessitates auxiliary means such as, for example, a one-way clutch and, as a result, automatically increases the size of the oil damper. In the worst case, this increase of size possibly renders the oil damper unsuitable for the intended use.
Further, the viscous oil such as silicone oil which is used in the storing chamber is susceptible of the influence of the change of temperature under the working conditions of the oil damper. In the construction in which the braking force is derived exclusively from the viscous resistance of oil as in the conventional oil damper, therefore, the torque of rotation varies in accordance with the temperature variation under the working conditions of the oil damper and the oil damper can no longer be expected to operate stably. Moreover, since the amount of the viscous oil to be placed in the storing chamber is necessarily large, the oil damper entails the disadvantage that the contained oil tends to leak from the oil damper in consequence of thermal expansion of the oil.
Another damper resorting to resilient pressure has been proposed in Japanese Utility Model Publication No. 57-49216.
The prior art damper, though not specifically illustrated herein, differs in idea from the conventional oil damper which makes use of the viscous resistance of oil. Specifically, it has a construction such that a plurality of J-shaped metallic leaf spring members are radially disposed in a rotor set rotatably in place inside a storing chamber of a housing and that the curved leading terminal parts of the J-shaped leaf spring members are kept in direct sliding contact with the inner wall surface defining the storing chamber of the housing. The opening speed of the ashtray case is braked by allowing the leaf spring members to move in company with the rotor thereby adding to the frictional force to be generated between the curved leading terminal parts of the leaf spring members and the inner wall surface of the storing chamber. Conversely, the ashtray case is pressed into the frame by decreasing the frictional force generated between the cured leading terminal parts of the leaf spring members and the inner wall surface of the storing chamber.
The prior art damper, therefore, has absolutely no use for the incorporation of viscous oil and has absolutely no possibility of succumbing to the influence of temperature change or entailing oil leakage. In terms of the convenience of use, the prior art damper is advantageous over the conventional oil damper since it is theoretically capable of varying the torque of rotation by virtue of the direction of rotation of the rotor without requiring use of auxiliary means such as, for example, a one-way clutch.
Since the prior art damper adopts a construction requiring the curved leading terminal parts of the J-shaped leaf spring members to be kept in direct sliding contact with the inner wall surface of the storing chamber, however, it is fated to require the component parts thereof to be highly accurate relative to one another. Only naturally, therefore, the work of assembling the component parts turns out to be very troublesome. In commercial production of the prior art damper, the possibility of the braking force being dispersed among a plurality of products is great. It also has a serious structural disadvantage that the individual leaf spring members, while moving in company with the rotor with the curved leading terminal parts thereof kept in sliding contact with the inner wall surface of the storage chamber, undergo stick slip and, in the worst case, get locked in situ and cease to produce smooth motion.
By this reason, the prior art damper which makes use of this resilient pressure has not been easily reduced to practice from the realistic point of view, though it enjoys the advantage not found in the oil damper.
In the light of the problems encountered by the conventional dampers as described above, the main object of this invention is to provide a rotary oil damper which enables the torque of rotation to be varied in the normal and reverse directions of rotation and defies the influence of temperature change.